Dyeing fabrics containing cellulose acetate fibers with a vat dye in reduced alkaline state and 30 to 80% of a liquid swelling agent



Patented Dec. 23, 1952 UNITED STATES PATENT FFICE George Donald Sutton, Marple, England No Drawing. Application March 20, 1947, Serial No. 736,122. In Great Britain October 8, 1946 9 Claims.

This invention relates to improvements in the colouration of textile yarns and fabrics composed wholly or partially of the form of cellulose acetate known as secondary or acetone soluble acetate.

In the following specification and claims the term cellulose acetate means the aforesaid form of cellulose acetate.

It is well known that it is difiicult or impossible to obtain deep shades on cellulose acetate with many dyestuffs used for dyeing other textile fibres, from aqueous dyebaths without deacetylation of the cellulose acetate. Many processes have been suggested for dyeing cellulose acetate with dyestufis which are insoluble in water or have little or no afiinity for the cellulose acetate and in the specification of English Patent No. 555,991 a process for dyeing cellulose acetate with such dyestuffs is described which consists in mechanically impregnating the material with a solution of the dye in a liquid comprising 70% to 80% by weight of a lower aliphatic alcohol, the remainder of the liquid being substantially water and after treatment drying the material.

Experiments show that the aforesaid process whilst giving satisfactory results when using dyestufis such as acid dyes or acetate dyes fails to produce deep shades if vat dyes are employed.

The specification of English Patent No. 583,349 claims a process for the colouration of cellulose acetate which comprises mechanically impregnating the material with a solution of a dye in a mixture of water and an aliphatic monohydric alcohol containing up to carbon atoms, the solution containing an inorganic thiocyanate which is a swelling agent for the cellulose acetate.

Among the dyestuffs referred to in the aforesaid specification are vat dyes either in the form of their leuco compounds or as salts of acid sulphuric esters of the leuco compounds.

The usual practice when dyeing with vat dyestuffs is to employ a caustic alkali such as caustic soda and a reducing agent (e. g. sodium hydrosulphite) in order to convert the vat dyestufi to its leuco form, but we find that if cellulose acetate is dyed in such a dyebath there is serious danger of saponification of the cellulose acetate taking place. On the other hand, if the conditions are so regulated during the treatment in the dyebath that no saponification of the cellulose acetate takes place then, after washing and soaping the material, no useful colouration of the cellulose acetate is obtained.

I have discovered and this discovery forms the basis of the present invention, that if a dyebath is made up with a vat dyestuff or dyestuffs converted to the leuco state by means of a weaker alkali than a caustic alkali such as ammonia, triethanolamine, or sodium carbonate, or if a caustic alkali is employed for producing the leuco compound but is removed from the bath before the cellulose acetate is treated therein, and a liquid organic swelling agent or agents "for cellulose acetate is added to the dyebath, then very strong colouration of cellulose acetate is obtained in a relatively short space of time (5-10 minutes) and at comparatively low temperatures (35-30 0.), with little or no saponification of the cellulose acetate.

Moreover I have found that, in order to obtain maximum depth of shade on the cellulose acetate it is necessary for the material to remain in contact with excess of the dye liquor for at least four minutes and preferably up to ten minutes and that deeper shades are produced when the cellulose acetate is in a tensionless condition in the dyebath than is the case when the material is under tension.

As before stated a caustic alkali may be employed for producing the leuco form of the dyestuff but in such case care must be taken to see that no caustic alkali is present in the .bath when the cellulose acetate material is treated therein as the rate of saponification of cellulose acetate by a caustic alkali appears to be considerably increased when a liquid organic swelling agent or agents is/are also present in the bath. This can be effected by adding a suificient quantity of sodium bicarbonate to convert the caustic alkali ,to a carbonate.

By a liquid organic swelling agent for the purpose of the invention is meant any of those alcohols, ketones or esters which are liquid at ordinary temperatures, and which have a swelling action on cellulose acetate and it will be understood that the amount of liquid organic swelling agent or agents present in the dyebath at a given temperature should be controlled so that no excessive shrinkage, delustration, or even .plasticisation of the cellulose acetate takes place.

The invention is applicable to the dyeing of yarns or fabrics composed wholly or partly of cellulose acetate whether by impregnation in a dye bath or by mechanical dyeing such as padding. In the latter case the material is padded with a dispersion of the unreduced vat dyestufi or dyestufis in water, and the fabric is then dried and subsequently treated in a :bath containing an alkali (other than a caustic alkali), sodium hydrosulphite and a liquid organic swelling agent or agents for cellulose acetate.

The invention is also applicable to printing yarns or fabrics composed wholly or partly of cellulose acetate in which case the cellulose acetate is printed with a printing paste containing an unreduced vat dyestuff or dyestuffs in a suitable thickening medium and after drying treated in a bath containing an alkali (other than a caustic alkali), a reducing agent and a liquid organic swelling agent or agents for cellulose acetate.

The invention has the further advantage that by using swelling agents for the cellulose acetate such as the lower aliphatic alcohols a fabric produced from cellulose acetate and cotton or regenerated cellulose can be dyed in two shades depending on the ratio of swelling agent to water in the dye bath since a lower aliphatic alcohol does not act substantially as a swelling agent for cotton or regenerated cellulose and water is not substantially a swelling agent for cellulose acetate.

Furthermore it allows the cellulose acetate in a mixed fabric to be dyed to a deep shade leaving the cotton or regenerated cellulose undyed or substantially undyed and to dye subsequently the cotton or regenerated cellulose by normal methods using a dye stufi which has by these methods little or no affinity for cellulose acetate thereby producing attractive two colour effects.

The following examples are given as illustrations of the invention but the invention is not in any way limited thereto:

Example 1 A dyebath is made up as follows:

grammes of Caledon Yellow 3 GS paste, Colour Index No. 1132, is vatted with grammes of sodium hydrosulphite and cc. of 0.880 ammonia in 265 cos. of water at 50 C. for 5 minutes. 700 cc. of ethyl alcohol is then added, which reduces the temperature of the dyebath to approximately C. The pH of this dyebath is about 9.9.

A 100% acetate fabric is treated in this dyebath for 10 minutes. The fabric is then washed thoroughly in cold water, subsequentl in water at 50S0 C. and finally soaped at 60-70 in a bath containing 0.5 gramme per litre of soap. The material is then washed and dried.

A deep shade of yellow results.

Example 2 A dyebath is made up as follows:

5 grammes of Caledon Brilliant Red 3 BS paste, Prototype 296 is vatted as in Example 1 with the exception that the ammonia is replaced by an equivalent amount (7.25%) of triethanolamine 700 cc. of ethyl alcohol is then added. The pH of this bath at 30 C., is approximately 9.35 A 100% acetate fabric is treated in this dyebath at a temperature of approximately 30 C. for 10 minutes. The material is then washed, soaped, washed and dried as in Example 1.

A deep red shade results.

Example 3 A dyebath is made up as follows:

5 grammes of Caledon Brilliant Red 3 BS paste, Prototype 296, is vatted with 25 cc. of 0.880 ammonia and 15 grammes of sodium hydrosulphite in 425 cc. of water at 50 C. for 5 minutes. Then 150 cc. of cold water and 400 cc. of ethyl lactate are added. The pH, after the addition of the lactate, is about 9.65.

A acetate fabric is treated in this dyebath for 10 minutes at a temperature of approximately 30 C. The material is then washed, soaped, washed and dried as in Example 1.

A deep red shade results.

Example 4 A dyebath is made up as follows:

2 grammes of Caledon Jade Green 4 GP 300 paste (a mixture of Colour Index No. 1101 and Prototype 9) is vatted with 15 cc. of caustic soda at 102 Tw. and 15 grammes of sodium hydrosulphite in 215 cc. of water at 50 C. for 5 minutes. Then 24 grammes of sodium bicarbonate is added to the bath in order to convert the caustic soda into sodium carbonate and '70 cc. of cold water and 700 cc. of ethyl alcohol are then added to the bath.

A 100% acetate fabric is treated in this dyebath for 10 minutes at a temperature of approximately 30 C., the pH of the bath being 10.5. The material is then Washed, soaped, washed and dried as in Example 1.

A deep jade green shade results.

Example 5 A dyebath is made up as follows:

10 grammes of Caledon Blue RNS paste, colour Index No. 1106, is vatted with 25 grammes of sodium carbonate and 15 grammes of sodium hydrosulphite in 290 cc. of water at 50 C. for 5 minutes and 700 cc. of ethyl alcohol are added to the bath. The pH of the bath as so prepared will be about 10.6.

A 100% acetate fabric is treated in this dyebath for 10 minutes at a temperature of approximately 30 C. The material is then washed, soaped, washed and dried as in Example 1.

A full shade of blue results.

Example 6 A dyebath is made up as follows:

1.5 grammes of Caledon Brilliant Orange 0 RS paste (4:10 dibromo-anth-anthrone) is vatted with 25 cc. of 0.880 ammonia and 15 grammes of sodium hydrosulphite in 275.5 cc. of water at 50 C. for 5 minutes and 700 cc. of ethyl alcohol is added to the bath. The pH of the bath as so prepared is about 10.15.

A viscose warp, acetate weft, Jacquard woven fabric is treated in this dyebath for 10 minutes at a temperature of approximately 30 C. The material is then washed, soaped, washed and dried exactly as in Example 1. This produces a deep coral shade on the acetate weft leaving the viscose Warp substantially undyed.

If a two colour effect is desired the viscose warp in the material may then be dyed in the normal manner with solubilized vat colours, for example in a bath made up as follows:

1 gramme of Soledon Jade Green XS powder,

5 grammes of Soledon Yellow GS paste,

0.5 gramme of sodium carbonate,

15 grammes of sodium chloride, in 1 litre of water.

The fabric is immersed in this bath at a temperature of approximately 40 C. for 10 minutes. It is then removed from the bath and treated to develop the true shade in a bath made up as follows:

2 grammes sodium nitrite 20 cc. of sulphuric acid 168 Tw.

in 980 cc. of water for 30-60 seconds at a tern-perature of approximately 25 C.

Example 7 A dyebath is made up as follows: 5 grammes of Caledon Red Violet 2 RNS paste,

Color Index No. 1161, is vatted with 25 cc. of

0.880 ammonia and 15 grammes of sodium hydrosulphite in 215 cc. of water at 50 C. for 5 minutes.

105 cc. of cold water and 630 cc. of methyl alcohol are then added to the bath. The pH of this bath will be 10.2.

A 100% acetate fabric is treated in this dyebath for minutes at a temperature of approximately 30 C. The material is then washed, soaped, washed and dried as in Example 1.

A full red violet shade results.

Example 8 A dyebath is made up as follows:

5 grammes of Caledon Red Violet 2 RNS paste, Colour Index No. 1161, is vatted with 25 cc. of 0.880 ammonia and grammes of sodium hydrosulphite in 215 cc. of water at 50 C. for 5 minutes.

455 cc. of water and 300 cc. of diacetone alcohol are then added to the bath. The pH of the bath Will be 9.8.

A 100% acetate fabric is treated in this dyebath for 10 minutes at a temperature of approximately 30 C. The material is then washed, soaped, washed and dried as in Example 1.

A full red violet shade results.

Example 9 A dyebath is made up as follows:

grammes of Caledon Brilliant Red 338 paste fine, Prototype 9, is vatted with cc. of 0.880 ammonia and 15 grammes of sodium hydrosulphite in 455 cc. of water at 50 C. for 5 minutes and 350 cc. of ethyl alcohol and 150 cc. of diacetone alcohol is added to the bath. The pH of the bath will be 9.5.

A 100% acetate fabric is treated in this dyebath for 10 mins. at a temperature of approximately C.

The material is then washed, soaped, washed and dried as in Example 1.

A deep bright red shade results.

Example 10 A 100% acetate fabric is padded through a bath containing 40 grammes of Caledon Blue GCP Colour Index No. 1113 in 960 cc. of water, at a temperature of 40 C.

The pressure on the squeezing rollers in the padding mangle is adjusted so that the material takes up 80% of its own weight of the padding liquor. The material is then dried.

Subsequently the material is treated for 5-10 minutes in a, separate bath made up as follows:

25 grammes of sodium carbonate plus 15 grammes of sodium hydrosulphite are dissolved 400 cos. of water at a temperature of approximately 50 C. Then 600 cos. of ethyl alcohol is added to the bath and the temperature finally adjusted to -40 C. The pH at this temperature will be about 10.3.

6 After treatment in this bath the material is washed, soaped, washed and dried as in Example 1.

A full blue shade results.

Example .21 (printing) A printing paste is made up of:

Grammes Caledon Blue GCP Colour Index No. 1113 paste fine British gum (4 lbs. per gallon of water) Water A 100% cellulose acetate fabric is printed with the above paste by an usual printing method such as roller screen or spray printing and subsequently dried.

It is then treated in a separate bath as in Example 10 and subsequently, washed, soaped, washed and dried as in Example 1, no steaming being necessary after printing to fix the colour.

I claim:

1. A process for the colouration of cellulose acetate with a vat dyestuif, which process comprises treating the material in a dye bath having a pH between about 9.0 and about 11.0, which dye bath consists essentially of an aqueous solution of a vat dyestuff in an alkaline leuco state, an alkali less strongly basic than caustic soda, a reducing agent, and from 30% to of a liquid organic swelling agent for cellulose acetate the amount being sufficient to effect pronounced swelling of the cellulose acetate said treatment being carried out at temperatures between 20 C. and 40 C. for from five to ten minutes.

2. A process for the colouration of cellulose acetate with a vat dyestuff which process comprises mechanically applying a dispersion in water of the vat dyestufi in its unreduced form and subsequently treating the material at temperatures between 20 C. and 40 C. for from five to ten minutes in an aqueous bath having a pH between about 9.0 and about 11.0 and containing an alkali less strongly basic than caustic soda, a reducing agent, and from 30% to 80% of a liquid organic swelling agent for cellulose acetate, in proportions sufficient to effect a pronounced degree of swelling of the cellulose acetate.

3. A process for the colouration of cellulose acetate with a vat dyestuif which process comprises padding the material with a dispersion in water of the vat dyestuff in its unreduced form and subsequently treating the material at temperatures between 20 C. and 40 C. for from five to ten minutes in an aqueous bath having a pH between about 9.0 and about 11.0 containing an alkali less strongly basic than caustic soda, sodium hydrosulphite, and from 30% to 80% of a liquid organic swelling agent for cellulose acetate to swell the latter to a pronounced degree.

4. A process for the colouration of cellulose acetate with a vat dyestuff which process comprises padding the material with a dispersion in water of the vat dyestuif in its unreduced form and subsequently treating the material for from 5 to 10 minutes in a bath having a pH between about 9.0 and about 11.0, which bath consists essentially of an alkali less strongly basic than caustic soda, a reducing agent, and from 30% to 80% by weight of a liquid organic swelling agent for 'cellulosel'acetate :said treatment being carried out at temperatures between20 C. and 40 C.

5. A process for the colouration of cellulose acetate with a vat dyestuff, which process comprises treating the material with: a vat dyestuff in an alkaline leuco state, an alkali less strongly basic than caustic soda, a reducing agent, and from 30% to 80% of a liquid organic swelling agent for cellulose acetate to effect pronounced swelling of the cellulose acetate, the process being characterized in that at least the swelling agent is applied to the fabric in a completely liquid state; in that the pH of the alkali permitted to act upon the fabric is between about 9.0 and about 11.0; and that treatment in the liquid phase is continued for from five to ten minutes, at temperatures between 20 C. and 40 C.

6. A process according to claim in which the dyestufi before being applied to the cellulose acetate is first treated with an alkali at least as strongly basic as caustic soda, and the basicity is reduced by adding an alkali bicarbonate in sufficient amounts to react with substantially all of the free alkali first mentioned.

7. A process according to claim 5 in which 'the organic swelling agent is an alcohol which is liquid at normal temperatures.

8. A process according to claim '5 in which the organic swelling agent is a ketone which is liquid at normal temperatures.

'8 9. A process according to claim 5 :in which the organic swelling agent an ester which is liquid at normal temperatures.

GEORGE DONALD SUTTON.

REFERENCES CITED The following references are of record in the file of this patent:

OTHER REFERENCES Rayon Text. M0. for Sept. 1946, page (496).

Dyeing of Synthetic Fabrics, article by Choquette in Am. Dye. Rep. for May 21, 1 945, pages P212, P213. 

1. A PROCESS FOR THE COLOURATION OF CELLULOSE ACETATE WITH A VAT DYESTUFF, WHICH PROCESS COMPRISES TREATING THE MATERIAL IN A DYE BATH HAVING A PH BETWEEN ABOUT 9.0 AND ABOUT 11.0, WHICH DYE BATH CONSISTS ESSENTIALLY OF AN AQUEOUS SOLUTION OF A VAT DYESTUFF IN AN ALKALINE LEUCO STATE, AN ALKALI LESS STRONGLY BASIC THAN CAUSTIC SODA, A REDUCING AGENT, AND FROM 30% TO 80% OF A LIQUID ORGANIC SWELLING AGENT FOR CELLULOSE ACETATE THE AMOUNT BEING SUFFICIENT TO EFFECT PRONOUNCED SWELLING OF THE CELLULOSE ACETATE SAID TREATMENT BEING CARRIED OUT AT TEMPERATURES BETWEEN 20* C. AND 40* C. FOR FROM FIVE TO TEN MINUTES.
 2. A PROCESS FOR THE COLOURATION OF CELLULOSE ACETATE WITH A VAT DYESTUFF WHICH PROCESS COMPRISES MECHANICALLY APPLYING A DISPERSION IN WATER OF THE VAT DYESTUFF IN ITS UNREDUCED FORM AND SUBSEQUENTLY TREATING THE MATERIAL AT TEMPERATURES BETWEEN 20* C. AND 40* C. FOR FROM FIVE TO TEN MINUTES IN AN AQUEOUS BATH HAVING A PH BETWEEN ABOUT 9.0 AND ABOUT 11.0 AND CONTAINING AN ALKALI LESS STRONGLY BASIS THAN CAUSTIC SODA, A REDUCING AGENT, AND FROM 30% TO 80% OF A LIQUID ORGANIC SWELLING AGENT FOR CELLULOSE ACETATE, IN PROPORTIONS SUFFICIENT TO EFFECT A PRONOUNCED DEGREE OF SWELLING OF THE CELLULOSE ACETATE. 